The present invention relates to a valve-seat material, which is employed as material suitable for producing valve seats for vehicle-engine exhaust valves.
In the past years when lead-contained gasoline was usable as vehicle fuel, even at high temperatures the wear-resistance of the valve seat was not such a problem as we were worried about, since the metallic contact between the exhaust valve and the valve seat was softened due to attachment, against the valve seat, of the gasoline lead component.
However, at the present time, the use of non-lead gasoline is compulsory from a view point of exhaust-gas legal regulation in every countries. Under this condition, the effect of preventing the wear of the valve seat cannot be expected from the lead. An iron alloy containing cobalt is being used for valve seat application as a high-temperature-resisting material, which is superior in strength, wear-resistance or the like. However, the cobalt metal is to be likely to be short on the world scale, is unstable in supply and price, and abnormally rises in price. Metal materials using the cobalt are required to be improved.
Thus, a valve-seat material with less cobalt content therein is proposed in various ways. The conventional materials of this type were not suitable as the valve seat materials for a lead-contained gasoline engine or a L.P.G. engine, which was different, in combustion temperature or atmosphere, from a non-lead gasoline engine. The conventional materials were inferior in general-use property for the application to engines of various types.